1. Field of the Invention
This invention relates to the synthesis of nitrogen compounds and, more particularly, to the formation of cyanates.
2. Art Background
A number of cyanate compounds (for purposes of this disclosure, a term used generically for compounds having an OCN or NCO moiety such as cyanates or isocyanates) have significant commercial applications. For example, ammonium cyanate or its equivalent urea is employed in a number of large scale uses. Urea is used as a main constituent in fertilizers, as a monomer in the production of plastics, and as an ingredient in animal feed. The large quantities of urea used are synthesized commercially by contacting carbon dioxide and ammonia at high pressure, typically 200 to 400 atms. and at temperatures between 140.degree. to 210 degrees C. to form ammonium carbamate, which is then decomposed into urea and water with a yield of 50%. The high pressures and incomplete conversion of CO.sub.2 and NH.sub.3 necessitate the use of expensive, sophisticated reaction and separation equipment. Production of smaller quantities is, therefore, not fiscally acceptable.
Other cyanate compounds which are potentially useful for similar applications, e.g., manufacture of monomers for polymer production, are too expensive for large-scale production by presently available techniques. For example, isocyanic acid (HNCO) is typically prepared by the slow or even dropwise addition of an acid to potassium cyanate. Although this process does not present the manufacturing complexities of urea production, i.e., it requires only very simple equipment, it is obviously unsuitable for large scale applications.
Thus, some processes for manufacture of cyanate compounds are suitable for large scale production, but require extensive capital investment in equipment while other processes utilize simple, inexpensive equipment, but are not adaptable for large scale production. Reported attempts to combine the attributes of process simplicity and suitability for large volume production have not been entirely satisfactory.